#include "VRFramebuffer.h"

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <pthread.h>
#include <sys/prctl.h>
#include <assert.h>
#include <GLES3/gl3.h>
#include <GLES3/gl3ext.h>

/*
================================================================================

ovrFramebuffer

================================================================================
*/


void ovrFramebuffer_Clear(ovrFramebuffer* frameBuffer) {
	frameBuffer->Width = 0;
	frameBuffer->Height = 0;
	frameBuffer->TextureSwapChainLength = 0;
	frameBuffer->TextureSwapChainIndex = 0;
	frameBuffer->ColorSwapChain.Handle = XR_NULL_HANDLE;
	frameBuffer->ColorSwapChain.Width = 0;
	frameBuffer->ColorSwapChain.Height = 0;
	frameBuffer->ColorSwapChainImage = NULL;
	frameBuffer->DepthBuffers = NULL;
	frameBuffer->FrameBuffers = NULL;
}

bool ovrFramebuffer_Create(
		XrSession session,
		ovrFramebuffer* frameBuffer,
		const int width,
		const int height) {

	frameBuffer->Width = width;
	frameBuffer->Height = height;

	XrSwapchainCreateInfo swapChainCreateInfo;
	memset(&swapChainCreateInfo, 0, sizeof(swapChainCreateInfo));
	swapChainCreateInfo.type = XR_TYPE_SWAPCHAIN_CREATE_INFO;
	swapChainCreateInfo.usageFlags = XR_SWAPCHAIN_USAGE_COLOR_ATTACHMENT_BIT;
	swapChainCreateInfo.format = GL_RGBA8;
	swapChainCreateInfo.sampleCount = 1;
	swapChainCreateInfo.width = width;
	swapChainCreateInfo.height = height;
	swapChainCreateInfo.faceCount = 1;
	swapChainCreateInfo.arraySize = 1;
	swapChainCreateInfo.mipCount = 1;

	frameBuffer->ColorSwapChain.Width = swapChainCreateInfo.width;
	frameBuffer->ColorSwapChain.Height = swapChainCreateInfo.height;

	// Create the swapchain.
	OXR(xrCreateSwapchain(session, &swapChainCreateInfo, &frameBuffer->ColorSwapChain.Handle));
	// Get the number of swapchain images.
	OXR(xrEnumerateSwapchainImages(
			frameBuffer->ColorSwapChain.Handle, 0, &frameBuffer->TextureSwapChainLength, NULL));
	// Allocate the swapchain images array.
	frameBuffer->ColorSwapChainImage = (XrSwapchainImageOpenGLESKHR*)malloc(
			frameBuffer->TextureSwapChainLength * sizeof(XrSwapchainImageOpenGLESKHR));

	// Populate the swapchain image array.
	for (uint32_t i = 0; i < frameBuffer->TextureSwapChainLength; i++) {
		frameBuffer->ColorSwapChainImage[i].type = XR_TYPE_SWAPCHAIN_IMAGE_OPENGL_ES_KHR;
		frameBuffer->ColorSwapChainImage[i].next = NULL;
	}
	OXR(xrEnumerateSwapchainImages(
			frameBuffer->ColorSwapChain.Handle,
			frameBuffer->TextureSwapChainLength,
			&frameBuffer->TextureSwapChainLength,
			(XrSwapchainImageBaseHeader*)frameBuffer->ColorSwapChainImage));

	frameBuffer->DepthBuffers =
			(GLuint*)malloc(frameBuffer->TextureSwapChainLength * sizeof(GLuint));
	frameBuffer->FrameBuffers =
			(GLuint*)malloc(frameBuffer->TextureSwapChainLength * sizeof(GLuint));

	for (uint32_t i = 0; i < frameBuffer->TextureSwapChainLength; i++) {
		// Create the color buffer texture.
		const GLuint colorTexture = frameBuffer->ColorSwapChainImage[i].image;
		GLenum colorTextureTarget = GL_TEXTURE_2D;
		GL(glBindTexture(colorTextureTarget, colorTexture));
		GL(glTexParameteri(colorTextureTarget, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE));
		GL(glTexParameteri(colorTextureTarget, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE));
		GL(glTexParameteri(colorTextureTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR));
		GL(glTexParameteri(colorTextureTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR));
		GL(glBindTexture(colorTextureTarget, 0));

		// Create depth buffer.
		GL(glGenRenderbuffers(1, &frameBuffer->DepthBuffers[i]));
		GL(glBindRenderbuffer(GL_RENDERBUFFER, frameBuffer->DepthBuffers[i]));
		GL(glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height));
		GL(glBindRenderbuffer(GL_RENDERBUFFER, 0));

		// Create the frame buffer.
		GL(glGenFramebuffers(1, &frameBuffer->FrameBuffers[i]));
		GL(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, frameBuffer->FrameBuffers[i]));
		GL(glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, frameBuffer->DepthBuffers[i]));
		GL(glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, frameBuffer->DepthBuffers[i]));
		GL(glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, colorTexture, 0));
		GL(GLenum renderFramebufferStatus = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER));
		GL(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0));
		if (renderFramebufferStatus != GL_FRAMEBUFFER_COMPLETE) {
			ALOGE(
					"Incomplete frame buffer object: %d", renderFramebufferStatus);
			return false;
		}
	}

	return true;
}

void ovrFramebuffer_Destroy(ovrFramebuffer* frameBuffer) {
	GL(glDeleteFramebuffers(frameBuffer->TextureSwapChainLength, frameBuffer->FrameBuffers));
	GL(glDeleteRenderbuffers(frameBuffer->TextureSwapChainLength, frameBuffer->DepthBuffers));
	OXR(xrDestroySwapchain(frameBuffer->ColorSwapChain.Handle));
	free(frameBuffer->ColorSwapChainImage);

	free(frameBuffer->DepthBuffers);
	free(frameBuffer->FrameBuffers);

	ovrFramebuffer_Clear(frameBuffer);
}

void ovrFramebuffer_SetCurrent(ovrFramebuffer* frameBuffer) {
	GL(glBindFramebuffer(
			GL_DRAW_FRAMEBUFFER, frameBuffer->FrameBuffers[frameBuffer->TextureSwapChainIndex]));
}

void ovrFramebuffer_SetNone() {
	GL(glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0));
}

void ovrFramebuffer_Resolve(ovrFramebuffer* frameBuffer) {
	// Discard the depth buffer, so the tiler won't need to write it back out to memory.
	const GLenum depthAttachment[1] = {GL_DEPTH_ATTACHMENT};
	glInvalidateFramebuffer(GL_DRAW_FRAMEBUFFER, 1, depthAttachment);
}

void ovrFramebuffer_Acquire(ovrFramebuffer* frameBuffer) {
	// Acquire the swapchain image
	XrSwapchainImageAcquireInfo acquireInfo = {XR_TYPE_SWAPCHAIN_IMAGE_ACQUIRE_INFO, NULL};
	OXR(xrAcquireSwapchainImage(
			frameBuffer->ColorSwapChain.Handle, &acquireInfo, &frameBuffer->TextureSwapChainIndex));

	XrSwapchainImageWaitInfo waitInfo;
	waitInfo.type = XR_TYPE_SWAPCHAIN_IMAGE_WAIT_INFO;
	waitInfo.next = NULL;
	waitInfo.timeout = 1000; /* timeout in nanoseconds */
	XrResult res = xrWaitSwapchainImage(frameBuffer->ColorSwapChain.Handle, &waitInfo);
	int i = 0;
	while (res != XR_SUCCESS) {
		res = xrWaitSwapchainImage(frameBuffer->ColorSwapChain.Handle, &waitInfo);
		i++;
		ALOGV(
				" Retry xrWaitSwapchainImage %d times due to XR_TIMEOUT_EXPIRED (duration %f micro seconds)",
				i,
				waitInfo.timeout * (1E-9));
	}
}

void ovrFramebuffer_Release(ovrFramebuffer* frameBuffer) {
	XrSwapchainImageReleaseInfo releaseInfo = {XR_TYPE_SWAPCHAIN_IMAGE_RELEASE_INFO, NULL};
	OXR(xrReleaseSwapchainImage(frameBuffer->ColorSwapChain.Handle, &releaseInfo));
}

/*
================================================================================

ovrRenderer

================================================================================
*/

void ovrRenderer_Clear(ovrRenderer* renderer) {
	for (int eye = 0; eye < ovrMaxNumEyes; eye++) {
		ovrFramebuffer_Clear(&renderer->FrameBuffer[eye]);
	}
}

void ovrRenderer_Create(
		XrSession session,
		ovrRenderer* renderer,
		int suggestedEyeTextureWidth,
		int suggestedEyeTextureHeight) {
	// Create the frame buffers.
	for (int eye = 0; eye < ovrMaxNumEyes; eye++) {
		ovrFramebuffer_Create(
				session,
				&renderer->FrameBuffer[eye],
				suggestedEyeTextureWidth,
				suggestedEyeTextureHeight);
	}
}

void ovrRenderer_Destroy(ovrRenderer* renderer) {
	for (int eye = 0; eye < ovrMaxNumEyes; eye++) {
		ovrFramebuffer_Destroy(&renderer->FrameBuffer[eye]);
	}
}

/*
================================================================================

ovrApp

================================================================================
*/

void ovrApp_Clear(ovrApp* app) {
	app->Focused = false;
	app->Instance = XR_NULL_HANDLE;
	app->Session = XR_NULL_HANDLE;
	memset(&app->ViewportConfig, 0, sizeof(XrViewConfigurationProperties));
	memset(&app->ViewConfigurationView, 0, ovrMaxNumEyes * sizeof(XrViewConfigurationView));
	app->SystemId = XR_NULL_SYSTEM_ID;
	app->HeadSpace = XR_NULL_HANDLE;
	app->StageSpace = XR_NULL_HANDLE;
	app->FakeStageSpace = XR_NULL_HANDLE;
	app->CurrentSpace = XR_NULL_HANDLE;
	app->SessionActive = false;
	app->SwapInterval = 1;
	memset(app->Layers, 0, sizeof(ovrCompositorLayer_Union) * ovrMaxLayerCount);
	app->LayerCount = 0;
	app->MainThreadTid = 0;
	app->RenderThreadTid = 0;
	app->TouchPadDownLastFrame = false;

	ovrRenderer_Clear(&app->Renderer);
}

void ovrApp_Destroy(ovrApp* app) {
	ovrApp_Clear(app);
}

void ovrApp_HandleSessionStateChanges(ovrApp* app, XrSessionState state) {
	if (state == XR_SESSION_STATE_READY) {
		assert(app->SessionActive == false);

		XrSessionBeginInfo sessionBeginInfo;
		memset(&sessionBeginInfo, 0, sizeof(sessionBeginInfo));
		sessionBeginInfo.type = XR_TYPE_SESSION_BEGIN_INFO;
		sessionBeginInfo.next = NULL;
		sessionBeginInfo.primaryViewConfigurationType = app->ViewportConfig.viewConfigurationType;

		XrResult result;
		OXR(result = xrBeginSession(app->Session, &sessionBeginInfo));

		app->SessionActive = (result == XR_SUCCESS);
	} else if (state == XR_SESSION_STATE_STOPPING) {
		assert(app->SessionActive);

		OXR(xrEndSession(app->Session));
		app->SessionActive = false;
	}
}

int ovrApp_HandleXrEvents(ovrApp* app) {
	XrEventDataBuffer eventDataBuffer = {};
	int recenter = 0;

	// Poll for events
	for (;;) {
		XrEventDataBaseHeader* baseEventHeader = (XrEventDataBaseHeader*)(&eventDataBuffer);
		baseEventHeader->type = XR_TYPE_EVENT_DATA_BUFFER;
		baseEventHeader->next = NULL;
		XrResult r;
		OXR(r = xrPollEvent(app->Instance, &eventDataBuffer));
		if (r != XR_SUCCESS) {
			break;
		}

		switch (baseEventHeader->type) {
			case XR_TYPE_EVENT_DATA_EVENTS_LOST:
				ALOGV("xrPollEvent: received XR_TYPE_EVENT_DATA_EVENTS_LOST event");
				break;
			case XR_TYPE_EVENT_DATA_INSTANCE_LOSS_PENDING: {
				const XrEventDataInstanceLossPending* instance_loss_pending_event =
						(XrEventDataInstanceLossPending*)(baseEventHeader);
				ALOGV(
						"xrPollEvent: received XR_TYPE_EVENT_DATA_INSTANCE_LOSS_PENDING event: time %f",
						FromXrTime(instance_loss_pending_event->lossTime));
			} break;
			case XR_TYPE_EVENT_DATA_INTERACTION_PROFILE_CHANGED:
				ALOGV("xrPollEvent: received XR_TYPE_EVENT_DATA_INTERACTION_PROFILE_CHANGED event");
				break;
			case XR_TYPE_EVENT_DATA_PERF_SETTINGS_EXT: {
				const XrEventDataPerfSettingsEXT* perf_settings_event =
						(XrEventDataPerfSettingsEXT*)(baseEventHeader);
				ALOGV(
						"xrPollEvent: received XR_TYPE_EVENT_DATA_PERF_SETTINGS_EXT event: type %d subdomain %d : level %d -> level %d",
						perf_settings_event->type,
						perf_settings_event->subDomain,
						perf_settings_event->fromLevel,
						perf_settings_event->toLevel);
			} break;
			case XR_TYPE_EVENT_DATA_REFERENCE_SPACE_CHANGE_PENDING: {
				XrEventDataReferenceSpaceChangePending* ref_space_change_event =
						(XrEventDataReferenceSpaceChangePending*)(baseEventHeader);
				ALOGV(
						"xrPollEvent: received XR_TYPE_EVENT_DATA_REFERENCE_SPACE_CHANGE_PENDING event: changed space: %d for session %p at time %f",
						ref_space_change_event->referenceSpaceType,
						(void*)ref_space_change_event->session,
						FromXrTime(ref_space_change_event->changeTime));
				recenter = 1;
			} break;
			case XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED: {
				const XrEventDataSessionStateChanged* session_state_changed_event =
						(XrEventDataSessionStateChanged*)(baseEventHeader);
				ALOGV(
						"xrPollEvent: received XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED: %d for session %p at time %f",
						session_state_changed_event->state,
						(void*)session_state_changed_event->session,
						FromXrTime(session_state_changed_event->time));

				switch (session_state_changed_event->state) {
					case XR_SESSION_STATE_FOCUSED:
						app->Focused = true;
						break;
					case XR_SESSION_STATE_VISIBLE:
						app->Focused = false;
						break;
					case XR_SESSION_STATE_READY:
					case XR_SESSION_STATE_STOPPING:
						ovrApp_HandleSessionStateChanges(app, session_state_changed_event->state);
						break;
					default:
						break;
				}
			} break;
			default:
				ALOGV("xrPollEvent: Unknown event");
				break;
		}
	}
	return recenter;
}

/*
================================================================================

ovrMatrix4f

================================================================================
*/

ovrMatrix4f ovrMatrix4f_CreateProjectionFov(
		const float angleLeft,
		const float angleRight,
		const float angleUp,
		const float angleDown,
		const float nearZ,
		const float farZ) {

	const float tanAngleLeft = tanf(angleLeft);
	const float tanAngleRight = tanf(angleRight);

	const float tanAngleDown = tanf(angleDown);
	const float tanAngleUp = tanf(angleUp);

	const float tanAngleWidth = tanAngleRight - tanAngleLeft;

	// Set to tanAngleDown - tanAngleUp for a clip space with positive Y
	// down (Vulkan). Set to tanAngleUp - tanAngleDown for a clip space with
	// positive Y up (OpenGL / D3D / Metal).
	const float tanAngleHeight = tanAngleUp - tanAngleDown;

	// Set to nearZ for a [-1,1] Z clip space (OpenGL / OpenGL ES).
	// Set to zero for a [0,1] Z clip space (Vulkan / D3D / Metal).
	const float offsetZ = nearZ;

	ovrMatrix4f result;
	if (farZ <= nearZ) {
		// place the far plane at infinity
		result.M[0][0] = 2 / tanAngleWidth;
		result.M[0][1] = 0;
		result.M[0][2] = (tanAngleRight + tanAngleLeft) / tanAngleWidth;
		result.M[0][3] = 0;

		result.M[1][0] = 0;
		result.M[1][1] = 2 / tanAngleHeight;
		result.M[1][2] = (tanAngleUp + tanAngleDown) / tanAngleHeight;
		result.M[1][3] = 0;

		result.M[2][0] = 0;
		result.M[2][1] = 0;
		result.M[2][2] = -1;
		result.M[2][3] = -(nearZ + offsetZ);

		result.M[3][0] = 0;
		result.M[3][1] = 0;
		result.M[3][2] = -1;
		result.M[3][3] = 0;
	} else {
		// normal projection
		result.M[0][0] = 2 / tanAngleWidth;
		result.M[0][1] = 0;
		result.M[0][2] = (tanAngleRight + tanAngleLeft) / tanAngleWidth;
		result.M[0][3] = 0;

		result.M[1][0] = 0;
		result.M[1][1] = 2 / tanAngleHeight;
		result.M[1][2] = (tanAngleUp + tanAngleDown) / tanAngleHeight;
		result.M[1][3] = 0;

		result.M[2][0] = 0;
		result.M[2][1] = 0;
		result.M[2][2] = -(farZ + offsetZ) / (farZ - nearZ);
		result.M[2][3] = -(farZ * (nearZ + offsetZ)) / (farZ - nearZ);

		result.M[3][0] = 0;
		result.M[3][1] = 0;
		result.M[3][2] = -1;
		result.M[3][3] = 0;
	}
	return result;
}

ovrMatrix4f ovrMatrix4f_CreateFromQuaternion(const XrQuaternionf* q) {
	const float ww = q->w * q->w;
	const float xx = q->x * q->x;
	const float yy = q->y * q->y;
	const float zz = q->z * q->z;

	ovrMatrix4f out;
	out.M[0][0] = ww + xx - yy - zz;
	out.M[0][1] = 2 * (q->x * q->y - q->w * q->z);
	out.M[0][2] = 2 * (q->x * q->z + q->w * q->y);
	out.M[0][3] = 0;

	out.M[1][0] = 2 * (q->x * q->y + q->w * q->z);
	out.M[1][1] = ww - xx + yy - zz;
	out.M[1][2] = 2 * (q->y * q->z - q->w * q->x);
	out.M[1][3] = 0;

	out.M[2][0] = 2 * (q->x * q->z - q->w * q->y);
	out.M[2][1] = 2 * (q->y * q->z + q->w * q->x);
	out.M[2][2] = ww - xx - yy + zz;
	out.M[2][3] = 0;

	out.M[3][0] = 0;
	out.M[3][1] = 0;
	out.M[3][2] = 0;
	out.M[3][3] = 1;
	return out;
}


/// Use left-multiplication to accumulate transformations.
ovrMatrix4f ovrMatrix4f_Multiply(const ovrMatrix4f* a, const ovrMatrix4f* b) {
	ovrMatrix4f out;
	out.M[0][0] = a->M[0][0] * b->M[0][0] + a->M[0][1] * b->M[1][0] + a->M[0][2] * b->M[2][0] +
	              a->M[0][3] * b->M[3][0];
	out.M[1][0] = a->M[1][0] * b->M[0][0] + a->M[1][1] * b->M[1][0] + a->M[1][2] * b->M[2][0] +
	              a->M[1][3] * b->M[3][0];
	out.M[2][0] = a->M[2][0] * b->M[0][0] + a->M[2][1] * b->M[1][0] + a->M[2][2] * b->M[2][0] +
	              a->M[2][3] * b->M[3][0];
	out.M[3][0] = a->M[3][0] * b->M[0][0] + a->M[3][1] * b->M[1][0] + a->M[3][2] * b->M[2][0] +
	              a->M[3][3] * b->M[3][0];

	out.M[0][1] = a->M[0][0] * b->M[0][1] + a->M[0][1] * b->M[1][1] + a->M[0][2] * b->M[2][1] +
	              a->M[0][3] * b->M[3][1];
	out.M[1][1] = a->M[1][0] * b->M[0][1] + a->M[1][1] * b->M[1][1] + a->M[1][2] * b->M[2][1] +
	              a->M[1][3] * b->M[3][1];
	out.M[2][1] = a->M[2][0] * b->M[0][1] + a->M[2][1] * b->M[1][1] + a->M[2][2] * b->M[2][1] +
	              a->M[2][3] * b->M[3][1];
	out.M[3][1] = a->M[3][0] * b->M[0][1] + a->M[3][1] * b->M[1][1] + a->M[3][2] * b->M[2][1] +
	              a->M[3][3] * b->M[3][1];

	out.M[0][2] = a->M[0][0] * b->M[0][2] + a->M[0][1] * b->M[1][2] + a->M[0][2] * b->M[2][2] +
	              a->M[0][3] * b->M[3][2];
	out.M[1][2] = a->M[1][0] * b->M[0][2] + a->M[1][1] * b->M[1][2] + a->M[1][2] * b->M[2][2] +
	              a->M[1][3] * b->M[3][2];
	out.M[2][2] = a->M[2][0] * b->M[0][2] + a->M[2][1] * b->M[1][2] + a->M[2][2] * b->M[2][2] +
	              a->M[2][3] * b->M[3][2];
	out.M[3][2] = a->M[3][0] * b->M[0][2] + a->M[3][1] * b->M[1][2] + a->M[3][2] * b->M[2][2] +
	              a->M[3][3] * b->M[3][2];

	out.M[0][3] = a->M[0][0] * b->M[0][3] + a->M[0][1] * b->M[1][3] + a->M[0][2] * b->M[2][3] +
	              a->M[0][3] * b->M[3][3];
	out.M[1][3] = a->M[1][0] * b->M[0][3] + a->M[1][1] * b->M[1][3] + a->M[1][2] * b->M[2][3] +
	              a->M[1][3] * b->M[3][3];
	out.M[2][3] = a->M[2][0] * b->M[0][3] + a->M[2][1] * b->M[1][3] + a->M[2][2] * b->M[2][3] +
	              a->M[2][3] * b->M[3][3];
	out.M[3][3] = a->M[3][0] * b->M[0][3] + a->M[3][1] * b->M[1][3] + a->M[3][2] * b->M[2][3] +
	              a->M[3][3] * b->M[3][3];
	return out;
}

ovrMatrix4f ovrMatrix4f_CreateRotation(const float radiansX, const float radiansY, const float radiansZ) {
	const float sinX = sinf(radiansX);
	const float cosX = cosf(radiansX);
	const ovrMatrix4f rotationX = {
			{{1, 0, 0, 0}, {0, cosX, -sinX, 0}, {0, sinX, cosX, 0}, {0, 0, 0, 1}}};
	const float sinY = sinf(radiansY);
	const float cosY = cosf(radiansY);
	const ovrMatrix4f rotationY = {
			{{cosY, 0, sinY, 0}, {0, 1, 0, 0}, {-sinY, 0, cosY, 0}, {0, 0, 0, 1}}};
	const float sinZ = sinf(radiansZ);
	const float cosZ = cosf(radiansZ);
	const ovrMatrix4f rotationZ = {
			{{cosZ, -sinZ, 0, 0}, {sinZ, cosZ, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}}};
	const ovrMatrix4f rotationXY = ovrMatrix4f_Multiply(&rotationY, &rotationX);
	return ovrMatrix4f_Multiply(&rotationZ, &rotationXY);
}

XrVector4f XrVector4f_MultiplyMatrix4f(const ovrMatrix4f* a, const XrVector4f* v) {
	XrVector4f out;
	out.x = a->M[0][0] * v->x + a->M[0][1] * v->y + a->M[0][2] * v->z + a->M[0][3] * v->w;
	out.y = a->M[1][0] * v->x + a->M[1][1] * v->y + a->M[1][2] * v->z + a->M[1][3] * v->w;
	out.z = a->M[2][0] * v->x + a->M[2][1] * v->y + a->M[2][2] * v->z + a->M[2][3] * v->w;
	out.w = a->M[3][0] * v->x + a->M[3][1] * v->y + a->M[3][2] * v->z + a->M[3][3] * v->w;
	return out;
}

/*
================================================================================

ovrTrackedController

================================================================================
*/

void ovrTrackedController_Clear(ovrTrackedController* controller) {
	controller->Active = false;
	controller->Pose = XrPosef_Identity();
}